One known example of a printer is an ink jet printer in which liquid ink is ejected through multiple nozzles to form characters and graphics on a page. The print quality is dependent upon printer resolution and print head performance. To achieve reliable performance, the ink jet print head and the ink jet process are designed to precisely control ink jet output. By controlling the timing, placement and volume of ink jet output droplets, reliable, repeatable character performance and graphical performance is achieved.
A clogged print head nozzle adversely impacts the placement and volume of inkjet output droplets as the ink droplet may be deflected from its intended destination and less than all ink may escape the nozzle. A seldom used nozzle may get dried ink or contaminants lodged in its orifice. Hot and dry environmental conditions, for example, speed up the drying process and may cause nozzles to clog. Also, contaminants from the external environment or from the printing process may get lodged in a nozzle blocking an orifice. Such clogging may occur despite design efforts to minimize ink drying and maintain a clean print head environment. Accordingly, there is an ongoing need to provide methods and apparatuses for cleaning inkjet print heads.
Current ink jet printers include either scanning-type print heads in which the print head scans a page while ejecting ink droplets or page-wide-array (PWA) print heads which include thousands of nozzles that span generally the entire page-width. With both scanning-type print heads and PWA print heads, cleaning and servicing of the nozzles is typically achieved by moving the print heads to a servicing region where the nozzles are cleaned and capped. Because PWA print heads are generally held stationary relative to the media being printed upon, servicing of the PWA print head requires that the individual nozzles or pens be later precisely reregistered once again with respect to the media or the transports configured to move the media relative to the print head.
One known alternative to moving the PWA print head to a designated service area is to alternatively feed a cleaning media to the print head along the paper path. This method and apparatus are disclosed in U.S. Pat. No. 5,589,865, the full disclosure of which is hereby incorporated by reference.